In an attempt to convey what he sees as a threat to Israel's existence, Israel's Prime Minister Benjamin Netanyahu used a cartoon to illustrate how close he says Iran is to developing a nuclear weapon. In a speech at the United Nations General Assembly he asked the world to help stop them. NBC's Andrea Mitchell reports.

By Andrea Mitchell, NBC News

NEW YORK -- Israeli Prime Minister Benjamin Netanyahu demanded that a “clear red line” be set to stop Iran from gaining a nuclear weapon, telling the U.N. General Assembly that with a nuclear Iran, no one in the world would be safe.

In a speech at the U.N. Thursday, Netanyahu said that Iran will have enough enriched uranium to build a bomb by next summer. He said his "red line" to stop Iran from gaining nuclear weapons is to stop it from accumulating that uranium -- because it would impossible to know when Iran has achieved the next step: building a detonator to fire a weapon.

At the U.N. podium, the Israeli prime minister showed a cartoon-like picture of a child's version of a bomb -- and drew a red line to illustrate his ultimatum.

He said that he and Israel appreciated President Barack Obama's statement that the U.S. also would not let Iran get a bomb -- and that he is confident that together the U.S. and Israel can chart a path together.

But he was very tough on Iran, reciting a litany of terrorism by Iranian proxies around the world and saying that given Iran's aggression without nuclear weapons, if it got nuclear weapons, who'd be safe anywhere?

Richard Drew / AP

Prime Minister Benjamin Netanyahu of Israel shows an illustration as he describes his concerns over Iran's nuclear ambitions during his address to the 67th session of the United Nations General Assembly at U.N. headquarters Thursday, Sept. 27, 2012.

In his speech, he also compared a nuclear-armed Iran with a nuclear-armed al-Qaida -- and said the only way to prevent war is to draw that red line against Iran accumulating enough enriched uranium to create a bomb.

An August report by U.N. inspectors said Iran has stockpiled 91.4 kg (about 200 lbs.) of the 20 percent material.

According to the U.N. nuclear watchdog, around 25 kg (about 55 lbs.) of uranium enriched to a 90 percent purity level would be needed for a single nuclear weapon.

Israel, believed to have the Middle East's only atomic arsenal, sees a nuclear-armed Iran as a threat to its existence and has expressed frustration over the failure of diplomacy and sanctions to rein in Tehran's nuclear activity. Iran says it is enriching uranium only for peaceful energy purposes, not for nuclear bombs.

Obama warned Iran on Tuesday in his speech to the General Assembly that he would do what it takes to prevent Tehran from getting nuclear arms and that "time is not unlimited" for diplomacy to resolve the issue.

Iranian President Mahmoud Ahmadinejad said this week he did not take seriously the threat that Israel could launch a military strike on Iran's nuclear facilities.